The term “conductive pattern” refers to a conductive pattern comprising both an organic component such as a resin and an inorganic component such as a conductive filler.
Thus far, for the formation of such an organic-inorganic composite conductive pattern as described above, so-called “polymer-type” conductive pastes in which a resin and/or adhesive is mixed with a large amount of fine particulate silver flakes, copper powder or carbon particles have been put into practice.
Many of the practically used polymer-type conductive pastes can be to form a pattern by screen printing and are capable of yielding a conductive pattern when heat-cured (JP H02-206675 A and JP 2007-207567 A).
For the purpose of forming patterns of 100 μm or smaller with good accuracy, there have been disclosed an acid-etchable conductive paste (JP H10-64333 A) and photosensitive curable conductive pastes (WO 2004/61006).
However, in the screen printing methods disclosed in JP '675 and JP '567, it is difficult to form a pattern of 100 μm or smaller with good accuracy.
Further, to perform patterning of the conductive paste described in JP '333 by photolithography, there is a problem that a resist layer must be formed on a coating film and this leads to an increase in the number of necessary steps. In the methods described in WO '006, a fine pattern can be easily obtained by imparting a conductive paste with photosensitivity. In the method of WO '006, there are problems not only that the acryl(methacryl) equivalent must be reduced to allow conductivity to be exhibited. The conductive pattern obtained by that method is fragile, making it difficult to apply the conductive pattern onto a flexible substrate. Also, the conductive pattern has poor adhesion with glass and ITO (indium tin oxide) electrode arranged on a film substrate.
It could therefore be helpful to provide a photosensitive conductive paste and a conductive pattern production method capable of yielding a conductive pattern exhibiting strong adhesion with ITO on a substrate, can be finely patterned, exhibits electrical conductivity at relatively low temperatures and, under certain circumstances, has flexibility.